1. Field of the Invention
The present invention relates to a method of fabricating a field emitting tip and a field emitting tip made by such a method. The field emitting tip of the present invention can be employed in a flat panel display.
2. Description of the Prior Art
A flat panel display (FPD) can include a number of field emission devices (FED). Various fabrication techniques for manufacturing a cathode used in a FED have been proposed when manufacturing a FPD including a FED.
FIG. 1 illustrates the structure of a conventional FED. An anode plate 10 is provided to receive electrons 20 from a cathode 30. A metal ring 40, which focuses the electron emission, is provided.
FIGS. 2(a)-(f) illustrate a conventional process of manufacturing cathode 30 as shown in FIG. 1. The process begins with a bare silicon substrate 50. To form a cap 60, a small layer of SiO2 is deposited on the silicon substrate and then a layer of Si3N4 is provided thereon. As shown in FIG. 2(a), the layers of SiO2 and Si3N4 are patterned and subjected to a reactive ion etch (RI E) to form cap 60 for the field emission tip of the device.
An isotropic silicon etch is performed to remove a portion of silicon from the surface of substrate 50. As illustrated in FIG. 2(b), cap 60 protects part of silicon substrate 50 from the etch and a pyramid structure 70, which is a characteristic of the prior art field emission tip, is produced.
As shown in FIG. 2(c), after pyramid structure 70 is formed, portions of silicon surrounding the pyramid are etched. Thermal oxidation is then performed to sharpen the field emission tip, which leaves an oxidation layer 80.
As shown in FIG. 2(d), an insulating layer 90 is then deposited to a desired thickness by evaporation. After insulating layer 90 is formed, a mask material 120 is laid down and patterned to define the array edges and metal 100 is deposited to form a metal ring 110.
Finally, as shown in FIG. 2(f), mask 120 and cap 60 are removed along with the material formed on cap 60 and mask 120 during the process to form the field emission device having metal ring 110.
Hyung Soo Uh and Jong Duk Lee, xe2x80x9cNew Fabrication Method of Silicon Field Emitter Arrays Using Thermal Oxidation,xe2x80x9d J. Vac. Sci. Tech. B 13(2) pages 456-60 (1995) describes a similar process using a well region formed in a semiconductor substrate. FIGS. 3(a)-3(f) illustrate this process, where FIGS. 3(e) to 3(f) illustrate the overlying structure being lifted off by etching the oxide surrounding the tip using a buffered hydrofluoric acid (HF) solution.
These conventional processes to produce a field emitting tip, however, suffer certain deficiencies. For example, because the conventional processes use a thermal oxidation process to sharpen the tapered profile of the silicon field emitting tip, the processes are time consuming. Further, the thermal oxidation process is not easy to control and, thus, the degree of sharpness of a tip may be degraded due to uncertainties based on the degree of oxidation. Also, cap 60, which functions as a hard mask during the processes, may fracture if processing is not carefully controlled. As described, for example, in U.S. Pat. No. 5,753,130, a special kind of micro-sphere hard mask can be used in the formation of sharp tips in an attempt to alleviate this problem, but providing a special mask is undesirable.
Accordingly, the present invention is directed to a method of forming a semiconductor device, a method of operating a projection exposure apparatus, and a semiconductor device that substantially obviate one or more of the problems due to limitations and disadvantages of the prior art. To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention can comprise a method of forming a semiconductor device including forming a hole in a surface of a substrate, covering the surface with a layer of semiconductor material so that a valley is formed in the layer of semiconductor material above the hole, providing masking material in the valley, and etching the masking material and the layer of semiconductor material to form a portion of the layer into a structure having a peak above the hole.
In another aspect of the invention, a method of operating a projection exposure apparatus can include placing a first layer of exposure sensitive material on a first layer of material of a device, exposing the first layer of exposure sensitive material using a mask, removing portions of the first layer of material in accordance with the exposure of the first layer of exposure sensitive material, placing a second layer of exposure sensitive material on a second layer of material of the device, exposing the second layer of exposure sensitive material using the mask, removing portions of the second layer of material in accordance with the exposure of the second layer of exposure sensitive material, placing a third layer of exposure sensitive material on a third layer of material of the device, and exposing the third layer of exposure sensitive material using the mask.
In a further aspect of the present invention a semiconductor device includes a first layer of material having a hole in its upper surface, and a second layer of material covering the hole, wherein the second layer of material includes a peak structure that is disposed in correspondence with the hole in the upper surface of the first layer of material.
Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the embodiments of the invention and together with the description, serve to explain the principles of the invention.